1. Technical Field
This disclosure is related to microscopes adapted for use in charged-particle instruments, where the microscope provides multiple magnifications with a single objective lens.
2. Background
It is often desirable to optically monitor the processing of a sample inside the closed space of a charged-particle beam apparatus, such as a focused ion-beam microscope or scanning-electron microscope, or any other vacuum chamber lacking the capability to render an image with high magnification. The distance from the vacuum chamber wall to the sample imaging location, the limited space between the sample and the charged-particle beam pole piece, the limited number of ports available in the charged-particle beam apparatus and the necessity to keep the vacuum pressure unchanged make it difficult to find a reliable and simple solution to this problem.
In this disclosure, we solve these problems using a single-objective lens combined with a gradient index lens (also called a self-focusing rod lens) to provide images of a specimen with different magnifications to two or more cameras or imaging devices. We also disclose systems adaptable to existing nanomanipulators, so that the working distance from the specimen to the objective can be easily varied as the nanomanipulator moves the system toward or away from the specimen. Such a system would also preferably be integrated with light sources for illumination of the specimen The light delivered inside the vacuum chamber can be of any wavelength from the optical region of deep UV (starting from 190 nm) to far IR (up to 10 microns).